1. Field of the Invention
The invention in general relates to fluid detector probes for differentiating between a polar and a non-polar liquid and a gas, such as water, oil, and air, and in particular to a compact rugged probe that can be inserted into constricted areas.
2. Description of the Prior Art
Fluid detector probes that differentiate between polar and non-polar liquids and gases have been used for some time to detect hydrocarbon pollutants. They have become particularly important in detecting the presence of leaks in tanks containing gasoline or oil. See, for example, U.S. Pat. Nos. 4,116,045 issued to Bronson M. Potter, 4,221,125 issued to John N. Oliver and Louis M. Sandler, 4,442,405 issued to Raymond J. Andrejasich and Ralph A. Perry and United States Patent application Ser. No. 579,431 on an invention of Raymond J. Andrejasich.
The state-of-the-art detector probes, such as described in the Andrejasich references mentioned above, generally include a float which moves vertically along a guide wire in a pipe and a pair of polar-non-polar fluid monitoring elements mounted on the float. A reed switch is also mounted on the float, which reed switch responds to a magnet located at or near the bottom of float travel, to provide a fluid state signal indicative of whether the float is resting at the bottom of float travel or is floating, i.e. whether the detector probe is in a gas or a liquid.
While these detector probes have become progressively more reliable, they have remained bulky. Thus, such probes have not been employed in some locations, such as between the walls of a double-walled tank, where it would be highly useful to detect hydrocarbons. This has been a significant problem in the industry because correction of a leak in the inner wall of a double-walled tank is usually relatively inexpensive, as compared to the cleanup that can be required upon leakage through both walls. The prior art probes, in addition to being bulky, are susceptible to mechanical damage under rough handling or operating conditions.